In the Beat of the Moment
by XX00Meg00XX
Summary: "No. No, Castle. You promised to sing the song. I told you it was the only way, so sing it." An M-rated crack!fic, set somewhere in season 3.


_Here it is, my first shot at a crack!fic, let alone an M-rated one. This was inspired by a real life conversation that occurred between a group of my friends and I a few weeks ago. If you'd like to hear the story, feel free to private message me here or Dm me on twitter. It's a pretty hilarious story._

 **Disclaimer:I do not own Castle or the characters used in this story.**

* * *

 _ **Just a reminder that this is meant to be funny and it is rated M!**_

* * *

 **In the Beat of the Moment**

 _A mid-season 3 fic, because that's when I picture this being the most entertaining. You can decide exactly when. And for the purposes of this, no other exes exist at the time._

* * *

"Castle, sing it. You…have…to…sing…it," she pants, her words stuttered and labored as her chest heaves. A sheen layer of sweat coats Kate's skin, glistening with each rock of her body, with each thrust of his hips.

She's close. So close that she can taste the beginnings of her orgasm, but she'll never get there unless he sings the song. She never has before.

Castle stares down at her in disbelief, still trying to wrap his mind around how they actually got here in the first place and she can't possibly be serious, can she?

He lets his hand drop between them, his fingers finding her swollen clit with practiced ease that gives nothing away of the fact that this is their first time. He circles two fingers as he continues to thrust into her, but instead of falling over the edge of bliss, Kate only shakes her head at him.

"Sing it, please," she grits out, her eyes almost pleading with him.

"Kate, I don't think…"

"No. No, Castle. You promised to sing the song. I told you it was the only way, so sing it."

He huffs at her, clearing his throat as he prepares the sing the ridiculous song. In all of the crazy sexual situations he's been in, he can't recall ever having to do something like this just to get a woman off.

"Fine," he agrees, deflating a bit; though, his rhythm inside her never falters.

He starts soft and slow, hesitation evident in his voice. "She'll…be…comin' 'round the mountain when she comes," he pauses, because she has got to be kidding right now and is this really necessary? _This is ridiculous_. He sounds insane, certifiably insane. But if the look she's giving him is any indication, she's definitely serious and it's obvious that he's going to have to get more into the song to satisfy her.

"I really don't see how…"

"Castle!" she growls, her nails raking down his back. "Sing the damn song, or pull out and let me finish myself off, because I'm not going to come unless one of us sings it."

He stares at her in disbelief. Kate Beckett is naked and writhing under him, a breathtaking sight that he thought he'd never get the witness, but this isn't at all how he pictured making her come for the first time. It's definitely not how he wrote Nikki and Rook doing it. Oh well, if he's going to act the part of certifiably insane, he might as well go all out.

He increases the pace of his thrusts, picking up where he left off on the song. "She'll be comin' 'round the mountain when she comes…"

As he sings, his mind wanders back a week ago to the moment that set this entire situation in motion.

* * *

 **One week earlier…**

"Castle, staring is creepy, how many times do I have to tell you?" she huffs and pushes her chair back from her desk as she stands, stretching her stiff body.

Castle grins and pulls out his phone to try his hand at the newest Angry Birds update, not even realizing the real effect that his staring has had on her until he looks up again and catches a glimpse of where her hardened nipples are making an appearance against the material of her shirt.

His eyes widen, a snarky comment forming on his tongue before he thinks better of it because he's not entirely sure that she won't shoot him.

He may be purposely hovering closer to her these days, brushing his hand down her back when he thinks he can get away with it, countering her quips with sexual innuendos that would make his mother blush and, now, it's obviously going exactly the way he planned.

He has no idea, but he wants to.

He emerges from his reverie a few moments later only to find Beckett nowhere in sight, crooking his neck to look for where she might have escaped to. _That's odd_. He doesn't remember her telling him that she was going somewhere.

He searches the break room first, but no sign of her. Then, he glances into each interrogation room as he passes by. But, nope, she's not there either.

It's then that he gets an idea, but no; she wouldn't possibly do something like that at work knowing that anyone could catch her…would she? Is the perfectly stoic Detective Beckett more of an exhibitionist than she's let on?

Allowing his curiosity to get the best of him, per usual, Castle strolls down the hallway. He makes a right turn at the end and heads towards the locker room, but just as he's about to pass it by, thinking there's no way she'd be in there in the middle of the day, he hears a soft moan and _wait, is that singing?_

He presses softly against the door until it cracks open, allowing him to hear better without actually seeing inside right away. And _oh my god_ , he knows that voice. Kate Beckett is singing and moaning in the locker room at the Twelfth precinct.

He eases the door open wider, slipping inside quietly before shutting it back, making sure that no one has seen him go in. He creeps further into the locker room, tiptoeing around the corner before he spots her, propped against the lockers in the far back corner of the room and his jaw drops.

Kate is naked from the waist down, her legs spread perfectly apart, allowing him a clear view of her hand, her slender fingers working rapidly in and out as her thumb circles her clit.

And all of that would be the hottest thing he's ever seen; well, actually, it is the hottest thing he's ever seen, but the fact that she's currently singing as she's getting herself off has him scratching his head and more than a little amused.

But it's not just the singing, it's _what_ she's singing.

Kate Beckett is masturbating to the tune of " _She'll Be Comin' 'Round the Mountain_." He doesn't know whether to be aroused or amused.

And then she gets to the climax of the song, just as she's…well—just as she's reaching her own climax and surprisingly, she comes hard, her perfectly held note turning to a pleased moan of pleasure.

That's when Castle makes his mistake; though, he may not see it as one later on.

He fails to hide his amused and equally aroused gasp, quickly pressing his hand over his mouth just as Kate looks up, her eyes meeting his, fire immediately burning behind her hazel irises.

"Castle! What the hell? What are you doing in here?" she asks, breathless and _hmm, is that embarrassment lacing her tone?_ She pulls her hand from between her legs, pressing them together to shield herself from his eyes. It makes no sense, he's already seen everything, has already _heard_ everything.

Castle takes a daring step closer to her, holding his hands up in mock surrender.

"You disappeared and I was looking for you. I didn't mean to…uh, interrupt your…well, what do you call that anyway? Because I was always under the impression that masturba…"

"Castle!" she scolds again, cutting the rest of his words off. "Turn around."

He hesitates.

"Turn around or so help me, I will shoot you as soon as I get my clothes back on."

"If you're going to shoot me, could you at least tell me the story behind that song first?" he asks, knowing that he's walking a fine line at the moment, but pushing anyway.

"No, Castle. It's none of your business and what you saw needs to be something that you forget. Right now," she growls from somewhere behind him and he takes a chance on turning back around, disappointed to find her fully clothed again.

"There's no way I'm ever going to forget any of that," he says, walking closer to her, relishing in the way she watches him with wide eyes.

"Tell me, Kate, why did you have the sudden need to get off? Why were you so aroused?"

He's stepping even closer, closing her in against the corner of the room as she backs away from him. Trapping Kate Beckett in a corner is never a good idea, but he quite likes the various possible outcomes of this one.

"I wasn't aware that we were close enough to tell each other when we're aroused," she snaps, her eyes diverting from his.

"Ah, but if that arousal is caused by the other person, well, that changes things."

"I'm not…I wasn't…you're not…" _Shit._

"You wanna try that again? Maybe make it a little more convincing this time?" he asks, his snarky tone pulling a signature eye roll from her.

"What do you want me to say?" she huffs, crossing her arms over her chest in defense. Such a typical Beckett thing to do.

"For starters? Tell me the story. Then we'll discuss the fact that I got you so hot and bothered at work that you got yourself off in the locker room."

"Why should I tell you?" she scoffs, shaking her head at him.

"Because, you know how much I love the story. And I have no doubt that I'm going to love this one. And since you didn't let me help you out, it's the least you can do."

He's pushing every fucking boundary that's ever existed between them and he's loving every second of it.

"Fine. Be at my place tonight at seven. And not another word about this until then," she says firmly, quirking her eyebrow just before she ducks under his arms and slips out of the locker room.

And that's what set the ball in motion.

* * *

He's standing outside her door two minutes before seven, checking his watch as he watches the seconds slowly tick by. As soon as it reads seven he's knocking, holding his breath in anticipation as he waits for her to answer.

Kate swings the door open with annoyed force, though he doesn't miss the slight upturn of her lips as he steps inside.

"I brought dinner," he says, holding up the white takeout bag in his right hand.

Kate nods, walking past him to the kitchen to get out some plates and forks. They settle on the couch with their Chinese, the awkward silence heavy between them until Castle can't stand it anymore.

"So…" he starts, glancing over at her.

She sighs and it's way more dramatic than would seem necessary if it wasn't her.

"I was sixteen," she starts, setting her plate down on the coffee table and pulling her legs up on the couch in front of her.

"All of my friends were talking about sex and orgasms and I'd never had one. I'd had sex, but never an orgasm," she says, her eyes searching his.

"I was no 'good girl', Castle. You already knew that so stop looking at me like that."

Castle smirks at her, but keeps quiet, wanting her to continue. He sets his own plate down on the table beside hers, making himself comfortable again before nodding for her to go on.

"Anyway, I started thinking that something was wrong with me so I made an appointment with my doctor. I made up some story to tell my mom so that she wouldn't go with me. When the doctor came in I didn't even know how to bring it up so I just dove right in. She told me that sometimes women need to associate the orgasm with something in order to coax it out. So I went home and did just that."

"And where does the song come in?" he asks because seriously, that's why he's here right now.

"I'm getting to it, Castle," she snaps, taking a deep breath and blowing it out as if she's telling him something completely serious and unrelated to the real conversation they're having.

"I came home and went straight to my room, locking the door even though my parents weren't home yet. I shed all of my clothes and stretched out on my bed, turning the TV on. It just so happened that an episode of The Andy Griffith Show was on. I started working myself up just as the characters started singing that song and I stopped thinking about the orgasm and focused on the song and it happened. So, ever since then, in order to come, I have to sing the song."

Castle waits for her to start laughing and tell him this entire thing in a joke because he just cannot picture a sixteen year old Beckett coming to the tune of that song for the first time on her bed.

But her face is about as serious as she is when she's interrogating a suspect.

"So, you've never had an orgasm unless that song is being sung?" he asks, trying to keep his tone neutral.

"No."

"So, if you're with a guy, he has to sing it, or…"

"Yes. One of us has to sing it. Which has presented some problems and rather embarrassing moments. There are reasons why I'm single, this is one of them," she says and he foregoes his amusement in favor of actually feeling sorry for her.

"Kate, I…"

"Don't. Don't say you're sorry or any of that mushy stuff. It is what it is, Castle."

"Do you find it a bit ironic that the words of the song kind of goes along with what you're actually doing when you sing it?" he asks, trying to suppress a smirk.

Kate rolls her eyes. "Don't make jokes, Castle."

"Well, for what it's worth, it doesn't change anything about my opinion of how sexy you are."

She offers him a smile accompanied by an eye roll. That's more like it.

"And yes, you turned me on at work. I was getting off in the locker room because of you and you're maddening touches that you think are subtle and your sexual innuendo and your constant staring."

"I have no idea what you're talking about," he says, ducking when she swats at his chest.

"How about I give you an idea then," she says suddenly, no trace of joking in her voice as she scoots closer to him.

"Kate?" he questions, completely unprepared for this.

"Oh come on, Castle. We've crossed so many lines tonight, you can't tell me that you don't want to cross this one."

"I…I do, but, Kate…"

"Stop talking," she says, swinging her leg over his lap as her lips slide against his.

* * *

And that's how they ended up here, her naked under him, begging him to sing the only song that will make her come.

"She'll be comin' 'round the mountain, she'll be comin' 'round the mountain, she'll be comin' 'round the mountain…"

"Yes, yes, Castle," she chants and, _oh my god,_ it's totally doing it for her.

"When she comes..." he sings, watching in shock as Kate's body bows, her chest heaving, inner walls fluttering around him as she comes, hard and fast.

He pumps into her a few more times, feeling her continuing to pulse around him as she pulls him over the edge with her.

He rolls to her side, staring up at the ceiling as he catches his breath, trying to wrap his mind around what just happened.

But then he looks at her, sprawled out on the bed, naked, chest heaving and he gets another idea, because he's had quite a bit of experience with the female body and there's something else he wants to try.

He rolls on top of her again, looking down at her wide eyes.

"Castle?"

"Stop talking, Kate," he repeats her words from earlier, cutting her off with the hard press of his lips. "You think you can't come without the song, I think you can."

And this time when he fucks her, he doesn't sing the song, doesn't do anything but drive her up, up, up, until she's mumbling incoherent words and begging for more.

Turns out, she totally can.

* * *

Castle walks into the precinct the next morning whistling a familiar tune, and he's never seen Kate Beckett blush before, but as the saying goes, there's a first time for everything.

* * *

 _Thanks to Ally for the constant encouragement and laughs while I was writing this, and as always, for the quick beta!_

 _So, how'd I do for a first time crack!fic writer? I'd love to hear your thoughts! xo_


End file.
